[clang] Remove shell requirements from tests
Most of these tests do not actually have a shell requirement. The shell
requirement ended up in the test either from cargo culting (from what I
can tell) or because the test authors actually meant to mark Windows as
unsupported. This prevents enablement of lit's internal shell within
clang.
Towards #102699.
Reviewers: rnk, efriedma-quic, Sirraide, petrhosek, ilovepi
Reviewed By: ilovepi
Pull Request: https://github.com/llvm/llvm-project/pull/156905
